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Crosslink density of oligourethane diols cured with amino resin at different temperatures
Author(s) -
Haseebuddin Syed,
Raju K. V. S. N.,
Yaseen M.
Publication year - 1997
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/(sici)1097-0126(199712)44:4<453::aid-pi848>3.0.co;2-f
Subject(s) - dichloromethane , polymer chemistry , molar mass , condensation polymer , diol , formaldehyde , chemistry , melamine , condensation reaction , condensation , materials science , solvent , organic chemistry , polymer , catalysis , physics , thermodynamics
Oligourethane diols were crosslinked with melamine formaldehyde ( N , N , N ′, N ′, N ″, N ″‐hexakis (butoxymethyl)‐2,4,6‐triamino‐1,3,5‐triazine). Their films were wetted with dichloromethane and the increase in dimensions of the swollen film under equilibrium swelling conditions was used to calculate crosslink density by using the Flory–Rehner equation. The molar mass between two crosslinks M c was also determined. The crosslink density of the coating is found to be influenced by a trans‐etherification reaction as well as by self‐condensation of the crosslinker. In formulations containing primary hydroxylated diol a major part of the crosslinker is consumed in a trans‐etherification reaction, whereas a part of the crosslinker undergoes self‐condensation in formulations containing secondary hydroxylated diols. The aromatic nature of 4‐methyl‐ m ‐phenylene diisocyanate (TDI) imparts rigidity while the aliphatic nature of 5‐isocyanato‐1‐(isocyanatomethyl)‐1,3,3‐trimethylcyclohexane (IPDI) results in flexibility of the backbone. The formulations containing 30% crosslinker and cured at 140°C for 20min are found to undergo completion of the major part of the reaction, indicating ideal conditions for their crosslinking from a commercial point of view. ©1997 SCI